1. Field of the Invention
The present invention concerns a scapholunate stabilization implant.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98
The scaphoid and the semilunate are two of the eight bones constituting the carpus of the hand. During a severe fall involving an impact on the wrist the intra-articular ligament connecting these two bones, called the scapholunate ligament, can suffer lesions such as a laceration, a tear . . . The failure of this ligament creates an instability which leads to an early arthrosis.
Interventions are available for the repair of this ligament depending on the extent of the injury:                interventions on the soft tissues;        fusions of bones.        
If the lesion is taken care of early enough by a surgeon, the latter can perform a suture or a ligamentary reinsertion which is only feasible if the ligament is still vascularized. Ligamentary reinsertion associated to capsulodesis is the technique presently used most often. Whatever technique is used, if it allows bringing the bones closer together and to reduce the scaphoid in an efficient manner, after having suppressed intra-articular fibrosis, the result can be good. However, these techniques on soft tissues are to be reserved for dynamic instabilities or for static instabilities that are easily reducible. Although it is possible with these techniques to restore the dynamics of the wrist and although the danger of the appearance of arthrosis has been avoided, the injured ligament never regains its initial capacities.
In case the lesion is not quickly looked after, the damage caused by friction of the scaphoid and the semilunate maybe irreversible and bone fusion needs to be considered. Bone fusions radically modify the mechanics of the wrist. Although bone fusions are reliable over the long term, these interventions present numerous disadvantages, the main one being the risk of pseudarthrosis. Furthermore, these interventions are often stiffening in flexion and in extension so that the patient loses a good part of these capacities of movement. Lastly, the risk of a new rupture after anatomical repair of the ligament is not negligible.
In another extreme case, ablation of the two bones may have to be considered.
Also known are prosthetic devices as replacement of the scapholunate ligament.
Most often, these devices are constituted by two plates intended to be anchored in each of the two bones to be reconnected, or to be fastened on the latter, and by a rod or a wire for making the connection of said two plates.
The disadvantage of such devices is that they are generally constituted, in part, by metallic elements. So there is a risk of osseous adherence. In fact, when an implant is present in an organism over a lengthy period, the bone has a tendency to “re-grow” on the implant and to partially cover it. It can then be impossible to remove it in its entirety which can be problematic, particularly during subsequent surgical interventions.
Furthermore, presently available devices require, in most cases, immobilization of the wrist with a splint or a plaster cast for a duration of 6 to 8 weeks, which prevents any premature mobilization and leads to a stiffening of the wrist.
To remedy these disadvantages, a scapholunate stabilization implant has been proposed in document FR-2951072.
This stabilization implant of a generally trapezoid shape capable of replacing the broken scapholunate ligament or of reinforcing the injured scapholunate ligament, is constituted by a plate of oblong shape made of a material having a capacity of elastic deformation the ends of which being provided with at least one hole for the passage of fastening screws and the central part of which presents an opening delimited by two opposing sides, a spring of predetermined stiffness connecting two distant points, preferably two opposite points of said sides, this spring being positioned along the diagonal, in said opening.
This device makes possible in particular:                supply of an implant which efficiently performs the functions of the scapholunate ligament,        rapid and precise installation of this implant,        feasibility of relative movements of the scaphoid and the semilunate, which is to say good functioning of the wrist.        
Utilization of this device has nevertheless made it possible to observe that it was desirable to make a few significant modifications with the aim of improving its performance.
For example, according to the implant described in document FR-2951072, the geometry of the implant is such that it does not support well the twisting movements in a direction perpendicular to the plane of the implant whereas the scaphoid and the semilunate are two bones that turn, one in relation to the other during certain movements of the hand.
One aim of the present invention is to provide orthopedic surgeons with a simple stabilization implant that is flexible, resistant and not very invasive, creating a mechanical connection between the scaphoid and the semilunate, reproducing the role of the scapholunate ligament, allowing to reestablish the initial mobility of the wrist bones (scaphoid and semilunate) and without the disadvantages mentioned above.
The device has been designed for the purpose of enabling the relative movements of the scaphoid and the semilunate while resisting the stresses imposed on them.